I have read her,e and heard elsewhere, that 2 mods is the limit before you need an FC upgrade to avoid detonation.

Why.

Please explain to me why mods like a catback and downpipe would cause detonation. These are exhaust upgrades that reduce backpressure. How do they then affect combustion?

I have a catback, pulley system and air intake system (Pettit). I just got my downpipe today. From what I have read I need to take care of the FC.

If so, what FC would you recommend, given possible future upgrades like Intercooler, turbo cooler (mister), etc?

 

You might want to try the 2nd gen forum. You would get more responds.

 

I think he means 'FC' as fuel computer.. but to answer your question you are right, exhaust mods do decrease back pressure. But, they also increase the amount of air your engine is ingesting and can typically raise the amount of boost your turbos are producing. Do you have a boost gauge yet? Running over stock boost on the stock ECU is not a good idea, and is usually governed by the 3-mod rule. As soon as you hit 3 'engine breathing' mods as I like to call them, you should seriously consider an ECU.. either that or a boost controller to keep your boost at stock levels. I will not go so far as to recommend an ECU, but I am using the PowerFC and love it so far.

Matt
93 SSM

 

I think he mean "Fuel Computer", instead of ECU (not FC as in the car).

PVerdieck, the 3-mod rule usually pertains to "air flow". When you begin to allow more air flow through the car, you are changing the air/fuel ratio. The ECU does not adjust to the A/F changes so in that sense adding more air without fuel can cause a lean situation.

However, with your modifications, I don't think you are of any risk of that running on the stock ECU. If you open up the exhaust any more, you should think about looking into an aftermarket ECU.